Production of cobalt



June 23, 1936.

F. L. BOSQUI PRODUCT ION OF COBALT Filed June 29, '1935 Patented June 23, 1936 UNITED STATES 2,045,212 PRODUCTION or comm Francis Lawrence Bosqui, NKana, Northern Rhodesia, assignor to Rhokana Corporation Limitcd, NKana, Northern Rhodesia Application June 29, 1933, Serial No. 678,288 l Claim. (Cl. 204-57) The present invention relates to the recovery of cobalt from material containing iron and cobalt, and more particularly from material containing copper, iron and cobalt. Aninstance of such material is a copper-cobalt ore or concentrate or furnace product containing iron, which is roasted and leached to produce a solution of the metals. Another instance is an alloy or mixture of copper, iron and cobalt such as may be obtained by reducing slag resulting from the smelting of copper ore containing iron and notable quantities of cobalt.

The object of the invention is to provide an effective electrolytic process whereby commercially pure cobalt may be cheaply obtained from a material containing iron and cobalt with or without copper or other metal which is lower in the electrochemical series than copper.

According to the invention, a solution of iron 7 and cobalt is obtained, from which the iron is removed. The resulting purified cobalt solution is supplied as katholyte to an electrolytic cell in which positive ions from the anode are excluded from the neighbourhood of the kathode. Such cell may be of the known kind in which the anode and kathode are separated by a partition which is porous to the extent of permitting flow of electrolyte. In said cell, also in the known manner, an outward flow of katholyte is maintained from the kathode compartment of sufiicient velocity to prevent the migration or difiusion of positive ions from the anode compartment into the kathode compartment. The katholyte is maintained at approximate neutrality, but with suflicient free acid to enable control to be maintained so that it does not pass over to basicity, which would cause cobalt hydrates to appear at the kathode.

The acid released by the electrolytic deposition of the cobalt is available for the dissolution of further quantities of the raw material. When such material is in metallic form, the dissolution is preferably efiected anodically. Moreover in order to conserve electrical energy, the anodic dissolution of the metals is preferably eifected in the same cell as the electro-deposition of the cobalt. This is rendered feasible by the aforesaid exclusion from the kathode of positive ions liberated at the anode, which prevents the metals,

.as they go into solution, from plating directly onto the kathode.

The anolyte produced by thus dissolving the mixed metals is continuously displaced from the cell and subjected to the selected treatment for the removal of it's iron content; being then acidified as far as may be necessary and returned to the cell as katholyte as above described.

Since all the metal thus anodically dissolved is not electro-deposited on the kathode owing to the removal from the solution oi. iron as above described and copper or other metal as described be anodically dissolved is measured by that which is actually electro-deposited, it is necessary to dissolve additional metal to make up the deficiency. This constitutes an electro-chemical balance, which term is employed in the claim.

This niay conveniently be efiected by providing make-up cells in which the electrolyte has a free acid content such that the dissolved iron and cobalt will not electro deposit from it, such as three to five grams per litre or over reckoned as sulphuric acid. The solution thus obtained is added to the anolyte eilluent from the deposition cell first described, so that itsiron content is removed before it enters the kathode compartment of suchdeposition cell.

When the raw material is metallic and contains copper or another metal lower than copper in the electro-chemical series, such copper or other metal is left to a large extent undissolved by the anodic dissolution above described, owing to the low acidity of the electrolytes employed and to, the presence of iron and cobalt, which are precipitants of it. In any event so much 01' the copper or equivalent other metal as enters the solution is precipitated with the iron at the iron precipitation stage.

A'practical method of carrying out the invention will be described with reference to the accompanying diagrammatic drawing.

When a copper ore contains both iron and oobalt the latter proceeds through the smelting operations with the iron and becomes automatically concentrated in the converter slag and also in the reverberatory slag in case 'the converter copper content since it is for the most part not dissolved bythe process 01' the'invention. A

composition well adapted for the purpose of the invention consists of:

Percent Copper- 20 Iron 10 Cobalt 65 Impurities 5 Thismetal is cast as anode suspended in the electrolytic cell 3 and connected to the positive pole 4 of a direct electric current supply system. The kathode plates 5 may plates 2 which are be of various materials such as rolled cobalt, iron,

copper or stainless steel. The kathodes are enclosed in boxes 6 the sides 1 of which are of fll'ter cloth. Cobalt sulphate is fed into these boxes:

from a storage tank 8 by means of pipes 9 having valves ID for controlling the rate of flow, whereby the liquid in] the boxes may be kept at a. higher level than the liquid outside them. It is desirable thus to maintain a hydraulic head in the box sufiicient to cause flow through the filter sides equal to about /2 litre per sq. foot of filter surface per hour. Flow at this rate substantially prevents the access of positive ions from the anolyte to the katholyte. ll indicates a circulating system by which the liquid in the box 1 is kept in movement, with the object of maintaining the katholyte of uniform composition and assisting deposition.

No acid need be added to the cell, the acid radicle liberated in the kathode compartment being carried through the walls I by the flowing electrolyte and effecting the corrosion of the anodes 2. A low current density is desirable from the point of view of limiting the tendency of positive ions to migrate or diffuse into the katholyte, and about 10 amps. per square foot may be employed. Under such conditions the anodes 2 are corroded; and their iron and cobalt contents go into solution. A small quantity of their copper content also goes into solution; but the bulk of it falls, as sludge, to the bottom of the cell 3. It is desirable to brush or scrape the anodes 2 from time to time to prevent accumulation of copper thereon, which would result in its going excessively into solution.

The liquid in the cell 3 flows to an outlet l2 whence it is conducted to the make-up cell l3. In this cell the anodes l4 are made of the mixed metal under treatment. The kathodes l5 are required only to act as conductors of electricity and may be copper plates. An essential feature of this cell is that the electrolyte I6 is too high in free acid to permit electro-deposition of the iron and cobalt dissolved from the anodes l4; and for this purpose an acidity equivalent to more than three grams per litre of free acid reckoned as sulphuric acid, is necessary. This is maintained by additions of fresh acid as indicated at I1. The current density in this cell may be the same as that in the cell 3.

The dissolving capacity of the make-up cell I3 is such as to add to the solution as much cobalt as is necessary to maintain the balance between deposition of cobalt in cell 3 and its dissolution in cells 3 and I3. The reinforced solution passes to a storage tank l8, whence it is delivered in batches to the agitation tank l9. To the latter are also supplied orddizing material, such as manganese di-oxide and acid; and basic material such as limerock. These contents of the tank are agitated by means indicated by 20 and maintained at an elevated temperature by steam coils 2| or the like.

By these means iron is precipitated in filterable form and the cobalt solution is thereafter separated from it in a filter 22; being then returned to the storage tank 8.

Here acid is added to it in just suflicient amount to ensure that the solution does not go basic in the cell 3, and the solution is allowed to flow into the boxes 6. There it becomes katholyte from which cobalt is electro-deposited onto the kathodes 5; the deposit usually taking a form which is easily detached after removal of the kathodes from the cell. The detached cobalt is washed and dried in stage 23 and melted in stage 24 to produce marketable metal.

I claim:

The process of electro-depositing cobalt from anode material containing iron, cobalt and copper, which consists in anodically corroding the anode material under conditions such that cobalt and iron go into solution in the electrolyte while the copper is mainly deposited as sludge, chemically precipitating iron from the electrolyte, and cathodically depositing cobalt therefrom, and maintaining the electro-chemical balance by anodically dissolving a further quantity of the same anode material in the electrolyte in a cell in which the conditions are such that cobalt and iron' go into solution but are not electro-deposited whilst copper is deposited mainly as sludge.

FRANCIS LAWRENCE BOSQUI. 

